Chemotactic activity of culture supernatants of free and encapsulated pancreatic rat islets towards peritoneal macrophages

Longterm efficiency of encapsulated pancreatic islet transplantation is lim ited by macrophagic reaction at the surface of biocompatible membrane. The aim of this work was to investigate the influence of soluble factors releas ed by free and encapsulated islets on macrophage chemotaxis. The culture me diums conditioned for 6 days by free and encapsulated rat islets were incub ated with peritoneal murine, rat allo and syngenic macrophages to study the ir migration. Culture supernatants of rat fibroblasts and acinar cells, glu cose-stimulated free rat islets and supernatants of free rat islets treated by heat and proteinase K were also tested for their chemotactic activity. Islets encapsulation decreased the chemotactic activity of culture medium c onditioned for 6 days by free rat islets on murine (1.66 +/- 0.20 vs. 3.10 +/- 0.23; p < 0.001, n = 5) and rat allogenic macrophages (1.63 +/- 0.21 vs . 4.70 +/- 0.36; p < 0.001, n = 9). There was no migration of rat macrophag es towards syngenic islets. Fibroblasts exhibited a very strong chemotactic effect as compared to acinar cells. Insulin was not involved in macrophage migration. Proteinase K treatment of culture supernatant of free rat islet s totally inhibited the chemotactic activity. After heating at 56 degrees C and 100 degrees C, this activity was reduced to 41 +/- 7% and 32 +/- 5% of the initial activity, respectively. In conclusion, pancreatic islet stimul ated macrophage migration by release of immunological specific proteins par tly retained by macroencapsulation.